In general, sheaths used to facilitate the insertion of devices, such as catheters, into the body are known. A catheter (or other medical device) can be inserted, with the use of a known sheath, percutaneously into the body, and the sheath can be torn off after insertion of the catheter. Tearable sheaths generally are referred to as peelable sheaths. There are also non-peelable sheaths. Peelable sheaths generally are used to introduce devices which are left in (or at least partially within) the patient after the procedure is completed, and a dialysis catheter is one example of a medical device that is left within the patient after a placement procedure. Non-peelable sheaths generally are used when the introduced device is removed at the end of the procedure.
Known peelable sheaths generally include a hub located at the proximal end of the sheath, and the hub can be manually grasped and pulled apart to permit the longitudinal severance of the hub and the sheath thereby to allow the removal of the sheath and hub from about the catheter extending therethrough and from the body. Such known peelable sheath/hub combinations typically are provided with a dilator, and the whole package generally is referred to as a peelable introducer system or simply an introducer system. Introducer systems with non-peelable sheaths also are known.
Some introducer systems, with the dilator inserted into and through the peelable sheath/hub, are designed to be advanced over a guide wire that is indwelling in a vein, artery, or other body cavity of a medical patient. In general, whether or not used with a guide wire, an introducer system is a medical device for insertion into the body (e.g., into a vein, such as the jugular vein, of a patient). In one possible use, the introducer system is placed into a patient's vein in order to allow a flexible catheter to be placed later within the same vein through the sheath/hub of the introducer system after the dilator component of the introducer system is removed from the sheath/hub component.
Various types of peelable and non-peelable sheaths and introducer systems are available from Boston Scientific Corporation (Natick, Mass.) and other companies. Boston Scientific Corporation provides certain peelable sheaths and introducer systems in its commercially-available Vaxcel PICC kits.
Some known introducer systems include a valve to provide a seal around the catheter introduced through the sheath.
In general, known valved peelable introducer systems include two basic components: (1) a peel-away sheath/hub, where the hub is fixed to the proximal end of the sheath; and (2) a more rigid dilator that is sized to slide and fit snugly into a lumen extending through the sheath/hub. The hub generally is provided either as two identical separate halves (split along the length of the hub) or as a single unit with scoring or perforations on both sides along its length to allow the sheath hub to be broken into two identical separate halves. The dilator has a proximal hub portion and a longer tubular portion, and a passage typically extends through the dilator such that the dilator can be passed over a guide wire, for example. The tubular portion of the dilator is designed to extend through the sheath and the hub, and the proximal hub of the dilator can lock (e.g., via a luer lock) onto the hub of the sheath. A valve is incorporated into the hub of the sheath, and the dilator passes through this valve when the dilator is inserted into and through the sheath/hub. The valve typically is a thin, disk-like membrane.
In a typical use, a known valved introducer system (with the dilator inserted into the sheath/hub and through the valve) is inserted into a patient's vein (usually over a guide wire that is already in the vein) up to the sheath's hub such that most or all of the sheath is within the patient's vein and most of the dilator also is within the patient's vein, while the hubs of the sheath and the dilator are outside of the patient's body. The dilator is then removed from the sheath and from the patient's body. With the dilator removed, the valve is supposed to close and prevent air from entering the vein, which generally would happen if the passage through the sheath was open, because of negative pressure in the vein. The catheter (or other medical device) is now supposed to be inserted through the hub, valve, and sheath and thus into the patient's vein.
Known valved introducer systems generally have at least two issues. First, the valve may be too rigid to allow flexible devices, such as flexible catheters, to be inserted therethrough. Many catheters do not have enough column strength or rigidity to be passed through a tight valve. Second, if the valve is sufficiently flexible to allow a flexible catheter to be inserted therethrough, the valve may become malpositioned after the dilator is removed. That is, the valve may not close properly after removal of the dilator, and thus the danger of air entering the body or blood leaving the body is not avoided by use of the valve.